Wednesday 6 June 2012 09.22 EDT
First published on Wednesday 6 June 2012 09.22 EDT

The president of Sri Lanka has been forced to cancel a keynote speech in the City of London after concerns about the threat of large demonstrations by Tamil rights groups.

Mahinda Rajapaksa, who has been accused of presiding over human rights abuses after allegations of war crimes by Sri Lankan armed forces, did however attend a lunch for the Queen, hosted by the Commonwealth secretary general at Marlborough House on Pall Mall, central London.

Hundreds of Tamil and human rights campaigners gathered outside Marlborough House to show their opposition to Rajapaksa's presence at the meal.

The Sri Lankan president was jeered as he swept through the main gate in a Range Rover. His car did not carry a flag because of security concerns.

The Queen spent a brief moment with Rajapaksa and appeared to fleetingly shake hands with him as she met guests at a reception in the Blenheim Saloon, inside Marlborough House.

Rajapaksa was seated on the table directly to the Queen's left with Babli Sharma, wife of the Commonwealth secretary general; the Namibian president, Hifikepunye Pohamba, and his wife; and New Zealand prime minister, John Key, and his wife.

Rajapaksa had been set to give the keynote speech at a special diamond jubilee meeting of the Commonwealth Economic Forum on Wednesday morning, but the event's organisers, the Commonwealth Business Council (CBC), said on its website: "After careful consideration, the morning sessions of the forum … will not take place." Tickets to the event cost £795 plus VAT.

A spokesman for Scotland Yard said it had agreed to guarantee the president's security but the CBC had "decided it was not in their interest to stage the event" because of the extent of the policing required and the likely disruption to the City of London.

Fred Carver, the campaign director of the Sri Lanka Campaign, welcomed the news, calling it a testament to the movement.

"It is absolutely not appropriate for President Rajapaksa to be feted by the Queen at the behest of the Commonwealth secretary general," said Carver.

"It is likely Assad [Bashar al-Assad, Syria's president] learned some lessons from the way the international community tolerated [many more] civilian casualties in Sri Lanka. What lessons will Assad learn from seeing how quickly the international community rehabilitates those responsible?"

Sen Kandiah, founder of the British Tamils Forum, said: "Common sense has prevailed. There is now enough evidence that allegations of war crimes in Sri Lanka lead directly to the president himself.

"That is why British government officials are reluctant to meet him. He is not welcome here."

The victim told the Guardian he was tortured over the space of 17 days after being deported from the UK last year.

His torturers accused him of passing on to British officials information about previous beatings at the hands of state officials and other human rights abuses to ruin diplomatic relations between the two countries.

The coalition is coming under increasing pressure to revisit a policy that suggests it is safe to return Tamils to Sri Lanka. Last week the high court halted the deportation of 40 people to the island at the last minute, citing human rights concerns.

In an in-depth interview, the former member of the rebel Tamil Tigers' intelligence service said he was tortured after the Home Office deported him and two dozen other asylum seekers in June 2011.

More than 70 UK border guards accompanied girls and men on the flight from Stansted airport last summer after a last-minute judicial review and his initial claim for asylum, based on previous evidence of torture, were turned down by UK authorities, he said.

Speaking through a translator, the victim, identified only as Hari for fear of further retribution by Sri Lankan authorities, said that six months after he was deported security personnel arrested him and beat him with rods, put petrol-filled plastic bags over his face and hung him by his feet with a nylon rope.

Hari's back displays a welter of scars and the Guardian has seen medical reports supporting his claims.

Hari managed to bribe his jailers and escape back to the UK via Russia and is now filing a second claim for asylum.

"I came here with a hope," he said. "I believed that the UK authorities would consider my case reasonably but, regardless of all my history and the evidence, they sent me back and I had to suffer again."

Last week, the UK government forcibly deported several other Sri Lankans, ignoring pleas from human rights organisations to halt flights in the face of mounting evidence that UK and European returnees have been tortured.

The Home Office has insisted it is safe to return Tamils to Sri Lanka after the end of a long civil war, and quotes a European court ruling that "not all Tamil asylum seekers require protection". However, officials are facing increasing pressure to change their policy.

In a dramatic turn of events last week, a senior high court judge halted up to 40 deportations from taking place as the plane waited on the tarmac.

Citing evidence from Human Rights Watch that returnees were being tortured on arrival, the judgment granted a last-minute reprieve.

Drafted by Justice Eady and seen by Channel 4 News, it is reported to have said: "The recent Human Rights Watch report, dated 29 May 2012, suggests that there may be new evidence relevant to the risk of ill treatment."

Human Rights Watch said that in one of the 13 cases it had taken up, the UK's immigration and asylum chamber had accepted that a woman who managed to make her way back to the UK in late 2010 after having been deported by Border Agency staff was tortured and raped on her forcible return to Sri Lanka.

A spokesman for the British Tamils Forum said the Human Rights Watch cases were likely to be "just the tip of the iceberg".